The invention relates to improvements in methods of and in apparatus for the application of adhesive spots or patches to intermittently transported objects, such as a series of successive blanks of paper, cardboard, plastic or the like. More particularly, the invention relates to improvements in methods of and in apparatus for applying (e.g., by one or more nozzles or analogous implements) spots or patches of adhesive to a succession of objects which are being advanced in stepwise fashion and in accordance with a predetermined pattern, preferably as regards the extent, the frequency and/or the rate of movement of successive objects along a predetermined path. Examples of objects which are being advanced or transported in the above outlined manner are blanks which are utilized in the tobacco processing industry for conversion into packs or other types of receptacles for smokers"" products, e.g., for arrays of plain or filter cigarettes, cigars, cigarillos or analogous rod-shaped products.
It is customary to employ valve-controlled nozzles in pasters which serve to apply (preferably or desirably) equal quantities of a suitable adhesive in various types of machines which are utilized in the tobacco processing industry. Patches, spots or continuous or interrupted strips of a suitable adhesive can be utilized for the making of longitudinal seams including the overlapping marginal portions of converted webs (envelopes or wrappers) of cigarette paper, tipping paper or the like. Those parts which are utilized to initiate or terminate the application of an adhesive to successive blanks of cigarette paper or the like (such parts can include, for example, mobile constituents of valves and/or valve-controlled nozzles) are invariably influenced by inertia which must be taken into consideration if the application of adhesive spots is to take place with a required or desired degree of predictability, uniformity and reproducibility. In other words, it is desirable and necessary to include, into the calculation of intervals during which a nozzle is to actually discharge adhesive from a suitable source onto successive objects of a series of successive objects, the intervals of succesive alternating accelerations and decelerations of the conveyor system for the series of objects as well as the intervals which elapse between successive assumptions by the valve or valves of its or their fully open and fully closed positions.
When the application of an adhesive is to take place in certain branches of the tobacco processing industry, the accuracy and predictability of such application are greatly influenced by the continuously increasing frequency at which the objects which are to receive spots or patches of adhesive must be advanced toward, past and beyond one or more adhesive applying stations. For example, patches of adhesive must be applied to selected portions of blanks which are to be converted into so-called soft or hinged-lid packs for arrays of cigarettes or the like. The patches must be applied to various tucks and/or flaps and/or panels and/or lids and/or walls in order to ensure that each adhesive-coated part will reliably adhere to a neighboring part when the conversion of a blank into a packet confining an array of cigarettes or the like is completed.
Presently known proposals to compensate for inertia of moving parts in the conveyor system and/or in the adhesive applying system for a series of objects (such as blanks of paper, cardboard or the like and hereinafter called blanks for short) include the resort to a preliminary or advance regulation. Such regulation takes into consideration certain specific values which are characteristic of moving parts (e.g., in a valve) and of their inertia in dependency upon various parameters, such as the nature and consistency of the adhesive, the pressure, the temperature and/or certain other variables. This is intended to ensure that, if the rate of transport of the blanks is at least substantially constant, the dimensions, the shapes and the locations of successively applied adhesive spots will at least approximate the desired values.
It has been ascertained that the presently known proposals to accurately meter the application of adhesive under the above outlined circumstances are often unsatisfactory, especially when accurately defined spots containing predetermined (optimum) quantities of a selected adhesive (e.g., a pasty adhesive) are to be applied to intermittently advanced blanks which are repeatedly accelerated, moved at full speed and thereupon decelerated at a high frequency, e.g., as required in a modern high-speed cigarette packing machine.
An object of the invention is to provide a method which ensures a highly predictable application of optimum quantities of an adhesive under circumstances which do not permit a sufficiently accurate distribution of optimum quantities of adhesive by resorting to heretofore known methods.
Another object of the invention is to provide a method which renders it possible to take into consideration all variables, or all relevant or important variables, which influence the rate of application of an adhesive paste during opening and closing of the valve or valves which is or are used to regulate the outflow of adhesive through the orifices of nozzles or analogous adhesive-dispensing implements.
A further object of the invention is to provide a relatively simple and readily practicable method which can be rapidly adapted to the desired or required circumstances of application of a selected adhesive.
An additional object of the invention is to provide a novel and improved apparatus for the practice of the above outlined method.
Still another object of the invention is to provide the apparatus with novel and improved controls for the device or devices which effect the dispensing of spots or patches of adhesive onto intermittently advancing objects in the form of paper or cardboard blanks or the like.
A further object of the invention is to provide novel and improved controls for the valve or valves which is or are utilized in the above outlined apparatus.
Another object of the invention is to provide a cigarette packing machine which embodies one or more apparatus of the above outlined character.
One feature of the present invention resides in the provision of a method of applying spots of adhesive to objects of a series of objects. The method comprises the steps of advancing the objects in a stepwise fashion in accordance with a pattern wherein a phase of zero speed is followed by a phase of acceleration, by a phase of advancement at an at least substantially constant speed and by a phase of deceleration back to zero speed, and discharging adhesive onto successive objects of the series (preferably by a nozzle of a valve including constituents having electrical and mechanical inertia) for periods of time ascertained on the basis of a plurality of parameters including a compensation interval for the inertia and a correction interval reflecting the pattern of advancement of the objects.
The method can further comprise the steps of monitoring at least the acceleration and deceleration phases of the pattern of advancement of the objects, generating signals denoting the monitored acceleration and deceleration phases, utilizing such signals to ascertain (e.g., to calculate) the correction interval, adding the correction interval to the compensation interval to thus determine the duration of the deceleration phase, and subtracting the correction interval from the compensation interval to thus determine the duration of the acceleration phase.
The advancing step can include placing the objects onto a stepwise advancing conveyor, and the monitoring step can include monitoring the speed of the conveyor.
The method including the just mentioned step can further comprise the step of monitoring the positions of objects on the conveyor.
The objects can comprise or constitute blanks (e.g., paper, cardbord and/or plastic blanks) of wrapping material.
The advancing step can comprise transporting the objects along an at least substantially horizontal path.
The method can further comprise the steps of establishing a source of adhesive, establishing a flow of adhesive from the source to the valve, and regulating the pressure of adhesive in the flow.
The discharging step can include applying to each object at least one elongated (e.g., rectangular) spot of adhesive.
Another feature of the invention resides in the provision of an apparatus for applying patches or spots of adhesive to successive objects of a series of objects. The improved apparatus comprises means for advancing the objects of the series in a stepwise fashion in accordance with a pattern wherein a phase of zero speed is followed by a phase of acceleration, by a phase of advancement at an at least substantially constant speed and a phase of deceleration back to zero speed. The apparatus further comprises at least one paster including an adjustable valve and a nozzle arranged to discharge spots or patches of adhesive onto successive objects on the advancing means (the valve includes constituents having electrical and mechanical inertia), and control means for the valve. In accordance with a presently preferred embodiment, the control means preferably includes means for causing the nozzle to discharge adhesive for periods of time which are ascertained as a function of a plurality of parameters including a compensation interval for the inertia and a correction interval reflecting the aforementioned pattern of advancement of the objects.
The control means can further comprise means for monitoring the advancement of objects and means for monitoring the positions of the objects relative to the nozzle during the application of adhesive to an object.
The apparatus can further comprise means for monitoring the rates of speed during the acceleration and deceleration phases and for transmitting signals to the control means.
Still further, the apparatus can comprise a source of adhesive, means for conveying adhesive from the source to the valve along a predetermined path (e.g., in a conduit), and means for regulating the pressure of adhesive in such path. The control unit can be arranged to determine the pressure of fluid in the path by way of the regulating means.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with numerous additional important features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompnying drawings.